1. Field of the Invention
The present invention relates to a rotating drum for reclaiming molding sand and a molding sand reclaiming apparatus for reclaiming molding sand from used sand which has been used for a casting mold. More particularly, it relates to a rotating drum for reclaiming molding sand and a molding sand reclaiming apparatus, in which extraneous matters sticking on used sand are peeled off by a mutual frictional contact between a fixed layer of used sand formed on the inner peripheral surface of the rotating drum by centrifugal force and used sand thrown in so as to reclaim sand from the used sand.
2. Prior Art
FIG. 10 shows a conventional apparatus disclosed in Japanese Patent Publication No. 2521765. FIG. 10(a) is an explanatory view of the whole apparatus, and FIG. 10(b) is an enlarged view of partition plates.
In FIG. 10(a), reference numeral 101 denotes a hopper for throwing molding sand in, 102 denotes an extruding member, 103 denotes a rotating grindstone, 104 denotes an opening, 105 denotes a molding sand tank for recycling, 106 denotes a molding sand extrusion passage, 107 denotes a driving motor, 108 denotes a storage section used to discard impurities, 109 denotes a dust collector transfer pipe, 110 denotes a depressurizing/pressurizing conveying pipe, 111 denotes a blow-up fan, 112 denotes a transfer passage, 113 denotes a screen member, and 116 denotes a transversely acting cylinder. In FIG. 10(b), reference numeral 114 denotes a partition plate, and 115 denotes a hole. Reference character A denotes molding sand, and a and b denote upper and lower space portions of the molding sand tank 105 used for recycling, respectively.
In the molding sand reclaiming apparatus shown in FIG. 10, a mass of molding sand A thrown into the hopper 101 is extruded from the extrusion passage 106 by the extruding member 102, and is ground by the rotating grindstone 103. Iron chips and core bars mixed in the mass of molding sand A are stored automatically in the discard storage section 108, and only particulate molding sand is screened by the screen member 113 in the transfer passage 112 and is transferred to the base of the depressurizing/pressurizing conveying pipe 110. The molding sand transferred to this portion is pushed up by the function of the air flow generated by the blow-up fan 111 and a dust collector, and stacked on the partition plates 114 provided in the molding sand tank 105 for recycling.
When the stacked amount on the partition plates 114 reaches a predetermined amount, the extrusion of the extruding member 102 is stopped, and then the two partition plates 114 are moved transversely. The holes 115 in the partition plates 114 are aligned by this transverse movement, so that the molding sand A drops from the lower space portion b onto the rotating grindstone 103 through the opening 104. The molding sand A is ground again, and is stored in the molding sand tank 105. The same operation is repeated until a predetermined degree of grinding is attained. Finally, the molding sand A is taken out of the molding sand tank 105 by means of a transfer pipe 119, and reclaimed molding sand A is taken out of a reclaimed sand storage tank 118. Besides, a xe2x80x9cmolding sand reclaiming apparatusxe2x80x9d disclosed in Japanese Patent Laid-Open No. 62-240135 is well known as an apparatus in which a plurality of rotating grindstones are provided in suspended molding sand.
As described above, the conventional molding sand reclaiming apparatus shown in FIG. 10 has an advantage that a series of processes to reclaim sand from the mass of molding sand A can be carried out continuously. However, such a configuration is used in this apparatus that the molding sand A extruded from the extrusion passage 106 is ground by the rotating grindstone 103. Therefore, the apparatus has a disadvantage that the rotating grindstone 103, which comes into contact with the molding sand and grinds it while being rotated, wears remarkably. In particular, in this conventional apparatus, a mass of molding sand A is extruded from the extrusion passage 106 by the extruding member 102 such as a cylinder mechanism, and is pushed compulsorily on the rotating grindstone 103, so that the outside diameter of the grindstone wears extremely.
If the outside diameter of the rotating grindstone 103 wears away, the radius of rotation of the rotating grindstone 103 for grinding decreases in accordance with proceeding of the wear, resulting in a decrease in the peripheral speed. Therefore, the grinding efficiency for reclaiming the molding sand decreases, resulting in the necessity of replacing the rotating grindstone 103. In order to replace the rotating grindstone 103, the operation of the molding sand reclaiming apparatus is stopped once, and then the apparatus is disassembled and the rotating grindstone 103 must be removed together with the driving shaft thereof. As a result, there arise problems in that the reclamation efficiency is decreased by troublesome replacing work of the rotating grindstone 103 and interruption of operation, and many spare rotating grindstones 103 for replacement must always be reserved according to the degree of wear. These problems also occur on the aforementioned xe2x80x9cmolding sand reclaiming apparatusxe2x80x9d disclosed in Japanese Patent Laid-Open No. 62-240135.
The present invention has been made to solve the above problems with the conventional apparatuses, and accordingly, an object thereof is to provide a rotating drum for reclaiming molding sand and a molding sand reclaiming apparatus in which a consumptive element such as the aforementioned rotating grindstone 103 is unnecessary, a high reclaiming performance is provided to keep the recovery percentage of reclaimed sand high, and the power consumption for operating the apparatus is kept low to restrain excessive equipment cost etc.
The present invention provides a rotating drum for reclaiming molding sand comprising a drum consisting of both a disk portion having a rotating shaft on its axis and a cylinder portion whose inner peripheral face is connected to the periphery of the disk portion, and a plurality of scattering holes formed in the cylinder portion to scatter molding sand from the inside of the drum to the outside thereof in accordance with the rotation of the rotating shaft.
Also, the present invention provides a rotating drum for reclaiming molding sand, in which the periphery of the disk portion is connected to an end of the cylinder portion to form a drum having a substantially U-shaped cross section.
Also, the present invention provides a rotating drum for reclaiming molding sand, in which the periphery of the disk portion is connected to a substantially middle position of the cylinder portion to form a drum having a substantially I-shaped cross section.
Also, the present invention provides a molding sand reclaiming apparatus comprising an agitation tank which is provided with a fluidized bed at the inner bottom thereof and also provided with a charging port for used sand and a discharging port for reclaimed sand on the side wall thereof; a rotating shaft driven by a driving source and disposed in the agitation tank; a rotating drum which is driven by the rotating shaft to agitate used sand charged into the agitation tank and peel off extraneous matters on the used sand; a classification tank which communicates with the upper part of the agitation tank and is provided with a dust collecting port; and an air pressure source to fluidize the used sand charged on the fluidized bed in the agitation tank and classify, in the classification tank, the used sand into two parts of the extraneous matters peeled off by the rotating drum and the reclaimed sand, characterized in that scattering holes for scattering the used sand are formed in a cylinder portion constituting the outside of the rotating drum.
Further, the present invention provides a molding sand reclaiming apparatus comprising a vertical cylindrical housing body provided with a suction port for dust and a discharging port for reclaimed sand at the upper part and the lower part thereof, respectively; a funnel-shaped hopper which is provided coaxially at the upper end of the body to supply used sand; a distributor which is disposed under the hopper to receive the supplied used sand and to drop the used sand distributively in the circumferential direction; a rotating drum having a U-shaped cross section which is disposed coaxially under the distributor to receive the used sand distributively dropped in the drum; a rotation driving source for rotating a rotating shaft which is fixed to the rotating drum; an annular shelf which is disposed around the rotating drum with a gap to receive the used sand received in the drum and scattered in accordance with the rotation of the rotating drum; and an air stream source which sends an air stream from the lower side of the rotating drum to blow the used sand upward in the body, characterized in that scattering holes for scattering the used sand are formed in a cylinder portion constituting the outside of the rotating drum, and the annular shelf is constituted by a lower shelf and an upper shelf for receiving the used sand ejected from the scattering holes and the edge of the cylinder portion of the rotating drum, respectively.